Field of the Invention
This invention relates to underground valves, such as utility valves and, more particularly, to a conduit assembly through which above ground access can be gained to a valve.
Background Art
Underground valves are used to selectively control utility supply, such as water, to individual residences and businesses. Each valve is typically situated several feet underground and is accessed through a vertical conduit assembly. In one known form, the upper end of the conduit assembly is closed by a cap with a separable plug that is threaded into place. The plug is separated to produce an entry opening to a passage extending downwardly to the valve. The plug is provided with a fitting to be engaged by a special tool, which thereby allows a level of control of access to the valve.
Existing conduit assemblies take a number of different forms. In one form, a cast housing, with an inverted cup shape, is placed over the valve and straddles the supply line and valve. The housing continues upwardly into a conduit, with a length selected so that the cap on the conduit is flush with grade.
In an alternative design, a conduit assembly has a fitting that is threaded directly to the underground valve. The conduit assembly defines a passage that extends continuously from the valve to an upper access opening.
With both of the above designs, elongate tools are directed from above ground through the conduit assembly passages to engage actuators on the valves. The tools control turning of the actuators in opposite directions to selectively open and close the valves.
Existing designs have some inherent problems, some of which are aggravated as the parts thereof corrode and/or are otherwise affected by environmental conditions.
One problem is a result of the manner in which the upper cap and plug, that is a part thereof, are constructed. Typically, the plug is made from brass so that it is not prone to rusting. The threads on the brass plug mate with threads on another part of the cap, typically made from a dissimilar metal. That other metal is generally prone to rusting or corroding, which could cause the threads to bind, thereby inhibiting turning of the plug for separation. It may become necessary to exert a substantial torque upon the plug to effect separation thereof. This torque may cause another part of the conduit assembly to turn. Depending upon the particular construction, this turning may inflict damage upon the conduit assembly, the housing at the bottom thereof, the valve, and/or the supply line.
When this condition exists, the individual seeking to operate the valve has the option of either taking exceptional steps to avoid turning of any other part of the conduit assembly associated with the plug, or gambling that the plug will break free before the failure of any other part of the system under a large turning torque.
The former option represents a significant inconvenience, particularly when utilities budget very little time for their workers to effect access. The latter can have significant consequences, and in a worst case may necessitate a time-consuming repair that could involve replacement of one or more system parts. In an extreme case, the valve itself may have to be accessed, which involves digging around the conduit assembly to create an access opening wide enough to allow a worker to repair, or remove and replace, the damaged structure, potentially including the valve.
In the event the valve itself must be replaced, the utility may have to utilize an upstream shutoff that could inconvenience not only the immediately affected entity, but any entity supplied through an interconnected conduit network downstream of the shutoff.
The above problems may be aggravated by temperature and other weather conditions. For example, rain followed by freezing temperatures may further lock the system components and make separation of the access plug even more difficult.
Another problem that has been persistent is damage inflicted by ground expansion due to frost. The frost causes the material in which the conduit assembly is embedded to expand and produce an increasing wedging action between the cap and underground structure, including lower portions of the conduit assembly and the supply line. This may eventually lead to the failure of one or more parts, thereby requiring access to the underground region in the vicinity of the compromised structure so that necessary repairs can be effected.
Of particular concern with all existing systems is to avoid damage to the underground valves and associated supply lines. As noted above, repair and replacement of a valve and/or portions of the connected supply lines may require service interruption and/or expensive and time consuming repairs that are effected by excavating around the valve to allow direct access thereto. Valve/supply line damage may be inflicted by above ground turning forces imparted by workers, above ground impacts, in-ground movement of the conduit assembly components in response to ground shifting/settling, shifting of the conduit assembly components in response to expansion forces caused by frost, etc.
Ideally, these conduit assemblies would have the ability to absorb forces generated by the above actions and conditions in a manner that the valve and associated supply lines are not damaged and remain fully operational.
In spite of these inherent deficiencies with existing systems, the industry has continued to use conventional designs. The industry continues to seek out alternative designs that are economically feasible, while being reliable in terms of their operation, regardless of environmental conditions.